Can my recipient tell if I'm tracking the email I send?

You should generally assume "yes."

Written by Andrew Stewart Updated over a week ago

Streak won't display a notification or add any kind of messaging to your email, but as mail clients get more sophisticated and focused on privacy, it's possible that your recipient will be alerted of email tracking being attached to your message.

The majority of recipients won't notice by default, though, and will simply be asked to display images in the email thread if they have images turned off by default.